1. Field of the Invention
This invention pertains to small lightweight waterproof strip chart recorders that are intended to be carried by hand and located at places where an environmental variable is to be measured for short periods of time such as 60, 90 or 180 days.
2. Description of the Prior Art
U.S. Pat. No. 3,487,691 illustrates a portable waterproof temperature recorder of which this invention is an improvement. In the patented recorder the strip chart take-up spool is driven at a constant rpm requiring that the chart paper have non-linear time graduations to compensate for changes in the diameter of the chart on the take-up spool. The use of non-linear time graduated paper is undesirable. Secondly, in the patented chart recorder the chart which is removed at frequent intervals for inspection or replacement was also in a compartment which revealed the drive mechanism. Frequently the drive mechanism was bumped or tampered with inadvertently which made it out of adjustment causing the subsequently recorded data to be unreliable.